Background/Purpose: Current clinical trials in dermatomyositis (DM) are largely focused on muscle improvement, and use the Total Improvement Score (TIS) as the primary efficacy measure. The TIS consists of Patient Global Assessment (PtGA), Physician Global Assessment (PGA), Extramuscular Global Assessment (EMGA), Manual Muscle Testing (MMT), serum muscle enzymes, and Health Assessment Questionnaire (HAQ). TIS may contain redundant measures and lacks a skin-specific measure. Skin is a defining feature of DM that should be directly measured in the primary endpoint. This study evaluated a new composite outcome measure, the Dermatomyositis Outcomes for Muscle and Skin (DMOMS), which includes components of TIS and a skin-specific measure. DMOMS consists of improvement from baseline in MMT, PGA, and PtGA, all scored as in TIS with the exception of a 50% increase in weight for PtGA. It also includes the Cutaneous Dermatomyositis Disease Area and Severity Index-Activity (CDASI-A) score, weighted equally to the MMT score.

Methods: Data was collected from the lenabasum phase 3 trial in DM. All components of TIS and CDASI-A scores were collected at Baseline and at Week 52. Pearson’s correlation on TIS components tested for redundancy (r > 0.8). Additionally, patients that had at least a 10-point improvement in MMT scores or 11-point improvement in CDASI-A scores at Week 52 compared to Baseline were considered to be responders. To assess efficacy of TIS and DMOMS scores in capturing skin and muscle disease improvement, a Student’s t-test (p < 0.05) was used to compare mean percent improvement in scores for both responders (R) and non-responders (NR). 

Results: Ninety-six DM patients were included in the analysis, with a majority of the patients being female (77%) and self-identifying as Caucasian (87%). Their mean (SD) age was 53 (11) years. Pearson’s correlation on TIS components showed that PGA and EMGA were redundant measures (r=0.827).CDASI-A R (n = 36) vs NR had a mean improvement in TISof 47.2% vs 29.8% (p < 0.001) and a mean improvement in DMOMS of 63.6% vs 28.8% (p < 0.001). MMT R (n = 27) vs NR had a mean improvement in TIS of 49.4% vs 31.2% (p < 0.001) and a mean improvement in DMOMS of 65.7% vs 32.5% (p < 0.001).

Conclusion: Compared to TIS, DMOMS is a simpler composite score, with four versus six component measures, and does not contain the redundant measure of EMGA. DMOMS also contains a skin-specific measure scored equally to a muscle-specific measure and assigns greater weight to PtGAto reflect clinical benefit as assessed by patients. It provides about twice the treatment effect for R vs NR in both muscle and skin response, without any increase in score in NR. DMOMS is a more sensitive outcome measure to reflect improvement from baseline in DM and may be better suited to determine treatment effect in future DM clinical trials.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-revised-outcome-measure-for-dermatomyositis-clinical-trials-the-dermatomyositis-outcomes-for-muscle-and-skin-dmoms/